1,2,3,4-tetrachloro-hexafluoro-butane (also known as “A316”) is used as an intermediate compound in the synthesis of hexafluoro-1,3-butadiene (also known as “C4F6” or “HFBD”), a stable gas which is used in the semiconductor industry, in particular as etching gas for semiconductor fine processing.
Methods for the synthesis of hexafluoro-1,3-butadiene and its intermediate A316 have been already disclosed in the art.
US 2009/0216053 (SHOWA DENKO K.K.) discloses a process for producing hexafluoro-1,3-butadiene comprising (1) a step comprising allowing a compound having four carbon atoms each which bonds to an atom selected from the group consisting of a bromine atom, an iodine atom, and a chlorine atom, to react with a fluorine gas in the presence of a diluting gas in a gas phase, thereby preparing a mixture containing product (A), and (2) a step comprising eliminating halogens excluding a fluorine atom with a metal from the compound (A) prepared in step (1) in the presence of a solvent. The production process preferably comprises the step (1) of allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas in the presence of a diluting gas a gas phase thereby preparing a mixture containing 1,2,3,4-tetrachloro-hexafluoro-butane and a step (2) of dechlorinating 1,2,3,4-tetrachloro-hexafluoro-butane obtained in step (1) by a metal in the presence of a solvent.
Similarly, US 20110071325 (SHOWA DENKO K.K.) discloses a process for producing 1,2,3,4-tetrachloro-hexafluoro-butane, which comprises feeding fluorine gas to 1,2,3,4-tetrachlorobutane using plural reactors in the presence of a solvent and in the absence of a catalyst to allow the 1,2,3,4-tetrachloro-butane and the fluorine gas to react with each other, wherein a part or all unreacted fluorine gas discharged from one reactor is introduced into a reactor different from said one reactor.
U.S. Pat. No. 8,536,387 (SOLVAY SOLEXIS S.P.A.) discloses a process for preparing perfluoro-1,3-butadiene comprising the steps of (A) preparation of fluoro-halo-butanes of formula (V) CF2Y/—CFY//—CFY//—CF2Y/ in which Y/ and Y// identical or different may be H, Cl or Br, provided that they are not simultaneously H, starting with a chloroolefin having the formula (II) CY″Y═CY′Cl in which Y, Y′ and Y″ identical or different are H, Cl or Br, provided that they are not simultaneously H, and performing the following two steps: a fluorodimerization and a fluorination with elemental fluorine; and (B) dehalogenation or dehydrohalogenation of the fluoro-halo compounds of formula (V) to give the compound perfluoro-1,3-butadiene.
U.S. Pat. No. 2,716,141 (WILLIAM T. MILLER) 23 Aug. 1955 discloses a method for preparing aliphatic compounds completely substituted with chlorine and/or fluorine. More in particular, the method of preparing a perhalo butane comprises reacting at least one compound of formula CR1R2═CR3R4 with elemental fluorine at a temperature of less than 50° C., wherein each of R is selected from chlorine, fluorine, perfluoro acyclic groups and perfluorochloro acyclic groups.
Also, a general mechanism for the reaction of elemental fluorine with perhalo-olefins has been presented by MILLER, W. T., et al. The mechanism of fluorination. III. Fluorine atom reactions. The olefin dimerization reaction. Journal of American Chemical Society. Jun. 20, 1957, vol. 79, p. 3084-3089. The mechanism provides the formation of dimer addition products by the diffusion-controlled combination of free radicals which are produced in pairs with the intermediate formation of fluorine atoms.
WO 99/22857 (BRITISH NUCLEAR FUELS PLC) discloses a method of carrying out a chemical reaction between two fluids using a micro-reactor. Fluorination reactions are cited among a wide list of chemical reactions that are said that can be performed in a micro-reactor. However, first this patent application is silent about fluorodimerization reactions, which are known to be different from fluorination reaction. In addition, this patent application is silent about fluorination reactions starting from reagents bearing chlorine atoms. Indeed, it is known that this kind of reaction suffer from specific concerns. For example, it is known for example from MILLER, W. T., et al. The mechanism of fluorination. III. Fluorine atom reactions. The olefin dimerization reaction. Journal of American Chemical Society. Jun. 20, 1957, vol. 79, p. 3084-3089. that when chlorine-containing olefins varying amounts of by-products corresponding to substitution of chlorine by fluorine III and to the addition of chlorine by fluoride IV are usually formed.